1. Field of the Invention
This invention relates to lubricating oil compositions comprising organometallic additives useful to increase the rust inhibition, sludge dispersant, wear reduction and anti-oxidant properties of the lubricating oil.
2. Summary of the Art
Various metal chelating agents are known for solubilizing metals in nonaqueous systems. For example, in U.S. Pat. No. 4,397,244, a class of such chelating agents are disclosed which are synthesized by (1) reacting formaldehyde and an amino acid and (2) then reacting the resulting product, with a phenol. The metal chelating agent may be in the acid form or the alkali metal or ammonium salt thereof. The chelation of Cu(II) and Fe(III) ions with this chelating agent is specifically disclosed and while it is claimed that other metal ions may be chelated therewith, the identity of such other metals is not found in the patent. (It is reported in a trade brochure, published on one of the individual metal chelating agents disclosed in this patent, that nickel and cobalt may be complexed.) The chelation of other metal ions to provide oil-soluble complexes may be found in U.S. Pat. Nos. 4,069,249; 4,152,345 and 4,225,502; however the chelating agents of these patents are structurally different than the chelating agents of U.S. Pat. No. 4,387,244 and it is well known that the degree of chelating ability of chelating agents is not predictable, a priori, from the chemical structure of the chelating agent, alone.
Organometallic additives are many times incorporated into lubricating oils to provide lubricating compositions having special and improved properties. For example certain copper and lead compounds impart corrosion resistance to lubricating oils. Organoboron compounds provide extreme pressure, anti-wear and friction reducing properties. Organozinc compounds are also known wear reducing additives. However, the determination of whether an organometallic compound will "work", that is, will impart the desired properties when added to a lubricating oil is also unpredictable, with a reasonable degree of certainty, from the chemical structure of such organometallic compound alone.
Therefore, it is one object of this invention to provide lubricating oil compositions having improved corrosion and wear properties and stability to oxidation.
Additional objects, advantages and features of the invention will become apparent to those skilled in the art from the following description.